Problem of selecting combobox in JTable!!

Question

I click comboBox in jtable and choose one item
then move mouse away
and then click the comboBox again
It turns out to be strange:
the selectedItem of the comboBox changes the first item at once
I refered to the demo "TableRenderDemo.java" in http://java.sun.com/docs/books/tutorial/uiswing/components/example-swing/TableRenderDemo.java
I just wanna do things like that
but for some unknown reasons,I fail
I compared two codes but found nothing

Answer 1

here I'm giving a simple sample code. Refer this..
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;
import javax.swing.table.*;
import java.awt.*;
public class Class1 extends JFrame {
JScrollPane jScrollPane1 = new JScrollPane();
JTable editableTable1 = new JTable(3, 3);     
public Class1() {
try {          
JComboBox c = new JComboBox();
c.setEditable(true);
c.addItem("a");
c.addItem("b");
DefaultCellEditor cellEditor = new DefaultCellEditor(c);
TableColumn tc = editableTable1.getColumnModel().getColumn(0);
tc.setCellEditor(cellEditor);
this.getContentPane().setLayout(null);
jScrollPane1.setBounds(new Rectangle(25, 19, 330, 180));
this.getContentPane().add(jScrollPane1, null);
jScrollPane1.getViewport().add(editableTable1, null);
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent we) {
System.exit(0);
} catch(Exception e) {
System.out.println("Exception in Class1:"+e);
public static void main(String[] args) {
Class1 class1 = new Class1();
class1.setSize(400, 400);
class1.setVisible(true);